Method of utilizing saline solutions



UNITED STATES PATENT OFFICE.

CHARLES N. IVAITE, OF RUMFORD, MAINE, ASSIGNOR TO THE ELECTRO- CHEMICALOOMPANY, OF RUMFORD FALLS, MAINE.

METHOD OF UTILIZING SALINE SOLUTIONS.

SPECIFICATION forming part of Letters Patent No. 558,240, dated April14, 1896.

Application filed March 19, 1894. Serial No. 504,242. (No specimens.)

To all whom it may concern.-

Be it known that I, CHARLES N. WAITE, a citizen of the United States,residing at Rumford, in the county of Oxford and State of Maine, haveinvented certain new and useful Improvements in Methods of UtilizingSaline Solutions, of which the following is a specification.

My invention has for its object an improved method for the utilizationof saline solutions. It is fully set forth in the following description,and its novel features are pointed out in the claim which is appendedhereto.

In the production of chlorin and of caustic by the electrolysis of achlorid of an alkaline base the solution of chlorid is subjected in anelectrolytic cell to the action of an electric current until theefficient working of the electrolytic cell is interfered with by thepresence of such a percentage of the hydrate or caustic as will decreasethe efficiency of the current beyond the limit at which the cell may beeconomically operated. \Vhen this occurs, the solution in thecompartment of the cell is removed and new solution supplied. Thesolution removed has lost only about onethird of the chlorid, and thusthere occurs aloss of a considerable portion of chlorid which cannot beeconomically employed in the cell owing to the presence of the hydrateor caustic.

In the production of chemical fiber which is employed in the manufactureof paperthe wood fibers or chips are boiled in a digester with theliquor containing caustic in solution. As a result of this treatment thegum and resin in the wood are converted into a soap and the fiber isleft free. The fiber is then removed and the soap liquor containing theexcess of caustic is evaporated and roast-ed in a rotary furnace,yielding black ash, which is recausticized with quicklime and used overand over again, enough efficient caustic being added to make up for theloss in recovery.

By means of my process I utilize the solution which is drawn from thecathode-coinpartment of an electrolytic cell, and which contains, asabove stated, the chlorid of the alkaline base and a considerablepercentage (usually six to eight per cent.) of the hydrate of the base,by employing the said solution for the treatment of the wood fiber inthe digesters in the production of chemical fiber. The presence in thissolution of the chlorid, ordinarily chlorid of sodium, does notinterfere with the use of the solution for this purpose. After the woodfiber has been boiled in this solution from the cathode-compartment ofthe electrolytic cell the fiber is Washed and the soapy liquorcontaining salt and the excess of caustic is evaporated and the residuumroasted. The black ash which results from the roasting contains salt andthe carbonate of soda and some impurities-such as coal, tarry matters,and the like. ably treat this ash by lixiviating with a limited amountof water, which results in the removal of the larger proportion of thecarbonate of soda. The latter being more soluble than the salt will gointo solution first. The salt and the remainder of the carbonate of sodacontaining the tarry matters, &c., are then dissolved and enoughquicklime is added to causticize the carbonate of soda. The resultingdirty solution is then run into the cathode side of the electrolyticcell and reelectrolyzed until there is again produced in it such apercentage of the hydrate or caustic as will interfere with theefficient and economic working of the cell by decreasing the efficiencyof the current beyond the economic limit. The dirty solution referred toshould be used only on the cathode side of the cell, since the presencein the anode-compartment of the cell of a small percentage of causticand of the tarry matters would destroy the efficient Working of thecell.

Instead of lixiviating the black ash to remove the greater portion ofthe carbonate of soda I may omit this step and instead dissolve thewhole of the black ash, adding to the solution quicklime to causticizethe carbonate and then proceeding as above described. By proceeding,however, without lixiviating the black ash a larger amount of causticwill be present in the dirty solution which is used in thecathode-compartment of the cell and less work can be done before itbecomes necessary to draw off the caustic, for reasons stated above.Whenin the operation of the electrolytic cell the solution in thecathode-compartment again contains a sufficient percentage of thehydrate to interfere I now preferwith the working of the cell, theliquor is again used in the digesters for the treatment of fiber and theprocess is repeated. By this method the chlorid, if the chlorid ofsodium be employed, can be used up entirely, only enough salt beingadded to make up for soda lost in the fiber from imperfect Washing, Without any loss of efiiciency in the electrolysis and With no Waste ofsalt.

In some localities Where paper-making is carried on salt is expensive,and in such 10- calities my process is particularly desirable andeffects a considerable saving.

What I claim is- That improvement in the utilization of saline solutionswhich consists in subjecting the solution to electrolysis in anelectrolyticcell,

